With a focus on Rio de Janeiro, I analyze the role of preservation planning in the favela within the context of modern city planning—just as the favela establishes its legitimate role in the city. In the setting of contemporary interventions, such as urban upgrading, tourism, and heritage designation, what might preservation look like in a built environment characterized by a rapid physical evolution and a history of social negligence? I look specifically at the communities of Morro da Providência, because it was the first informal settlement termed a favela in Brazil, and Santa Marta, because it is one of two favelas located within the boundaries of a UNESCO World Heritage Site in Rio de Janeiro. This research is significant because it can help make preservation more relevant to planning practices, but perhaps more importantly, it encourages the consideration of significance in informal settlements.